valve spec and fix


24 replies to this topic
  • Yzflier977

Posted March 22, 2016 - 05:35 PM

#1

Hey guys, I've got a 2009 YZ450 that I've put 130 hours on.  I bought it used and am not sure of the actual total hours on the motor.  Anyway I'm at that point where the middle intake valve has finally tightened up on me.  I've already shimmed that valve once so as I understand it, it's time to service the head/valves.  Before the bashing begins, yes I've searched the forum and have read so much that my eyes are about to cross.  I've reached out to Fastheads and Engine Dynamics for some prices but I would like to know what exactly do I need to have done?  I'm assuming seats replaced and new valves and keepers as cheap insurance.  I wouldn't think the guides need anything?  Springs maybe?  Motor is stock and I don't race it or ride it hard.  Any help is appreciated. 



  • 0bigsilver6

Posted March 22, 2016 - 05:45 PM

#2

Hey guys, I've got a 2009 YZ450 that I've put 130 hours on. I bought it used and am not sure of the actual total hours on the motor. Anyway I'm at that point where the middle intake valve has finally tightened up on me. I've already shimmed that valve once so as I understand it, it's time to service the head/valves. Before the bashing begins, yes I've searched the forum and have read so much that my eyes are about to cross. I've reached out to Fastheads and Engine Dynamics for some prices but I would like to know what exactly do I need to have done? I'm assuming seats replaced and new valves and keepers as cheap insurance. I wouldn't think the guides need anything? Springs maybe? Motor is stock and I don't race it or ride it hard. Any help is appreciated.

With that amount of hours I would rework the whole top end. New piston/rings. And completely redo the head with new valves, springs, keepers, guides, all of it. Just make sure the seats get touched up before installing new parts.

Edited by 0BigBlue7, March 22, 2016 - 05:49 PM.


  • Yzflier977

Posted March 22, 2016 - 05:54 PM

#3

With that amount of hours I would rework the whole top end. New piston/rings. And completely redo the head with new valves, springs, keepers, guides, all of it. Just make sure the seats get touched up before installing new parts.

Actually just did a top end with timing chain and tensioner about 32 hours ago.  Just happened to be valve time now. 



  • 0bigsilver6

Posted March 22, 2016 - 06:03 PM

#4

Actually just did a top end with timing chain and tensioner about 32 hours ago. Just happened to be valve time now.


Ahh ok. So is there 130 hours on all the valves then? Or did they get done 32 hours ago as well and one is just wearing really fast?

  • Mykle125

Posted March 22, 2016 - 06:09 PM

#5

I think he means that those are the original valves, or at least the ones he put 130 hours on.

Edited by Mykle125, March 22, 2016 - 06:10 PM.


  • Yzflier977

Posted March 22, 2016 - 06:15 PM

#6

I think he means that those are the original valves.

Correct, they are the original valves and I've put 130 hours on the bike and the previous hours are unknown.  I've checked them every quarter for the last year knowing they were going to start wearing at some point and it's finally here.



  • 0bigsilver6

Posted March 22, 2016 - 06:15 PM

#7

If this is the case, what he said^, you'd probably be best off just doing all the valves. I'm sure you could get away with just doing the one that is wearing, but why not just do them all while you have it apart? At the very least I would do new valve springs on all of them.

It's really up to you. They probably don't all NEED to be done, but I look at it as preventive maintenance. So it's just a matter of what you want to do, and what your pocket book can handle.

Edited by 0BigBlue7, March 22, 2016 - 06:19 PM.


  • Yzflier977

Posted March 22, 2016 - 06:21 PM

#8

If this is the case, what he said^, you'd probably be best off just doing all the valves. I'm sure you could get away with just doing the one that is wearing, but why not just do them all while you have it apart? At the very least I would do new valve springs on all of them.

Oh I intend to do new valves, seals and keepers (and likely springs).  I'm wondering about what to do to the head itself?  I'm assuming just seats and where to get that work done?  I'm going to check with my local dealer tomorrow and see who they use locally but wanted options for sending it off if anyone has recommendations?



  • Mykle125

Posted March 22, 2016 - 06:21 PM

#9

New valves and springs for sure, check the old ones for any sight of slapping or rubbing, and gauge whether u want to get the guides or seats done. I assume your buckets and cams look in decent shape?

Preventative maintenance gives you reliability and peace of mind!

Edited by Mykle125, March 22, 2016 - 06:23 PM.


  • 0bigsilver6

Posted March 22, 2016 - 06:24 PM

#10

Oh I intend to do new valves, seals and keepers (and likely springs). I'm wondering about what to do to the head itself? I'm assuming just seats and where to get that work done? I'm going to check with my local dealer tomorrow and see who they use locally but wanted options for sending it off if anyone has recommendations?


You probably won't have to do anything major to the head, other than having all the seats touched up by a machine shop before installing new valves. You will have to take the valves to the shop as well so they can match the seats to the valves.

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  • Yzflier977

Posted March 23, 2016 - 12:49 PM

#11

Well now the water is muddier than ever.  I talked to my local Yamaha dealership today and the guy at the service department said that as long as I can shim them I should (not a big fan of the kicking the can down the road method).  That's counter to everything I've ever read about valves tightening up.  Another dealer service department (not Yamaha) said replace the valves with steel ones and new springs and don't worry about the seats.  They said the valves are the wear item not the seats.  Fastheads gave me a price for head rebuild but their price was not attractive.  I would like to be able to get another 200+ hours out of this head rebuild so I'm leaning toward the fastheads option.  Anyone have any experience with them, positive or negative?



  • grayracer513

Posted March 23, 2016 - 03:03 PM

#12

I categorically disagree with the service guy's assessment.  If the center intake closed up for the second time, and has moved more than .10mm, it's not going to last very much longer, and it has become a failure risk.  He is right about the seats, provided you don't let the valve go too long.  The don't usually need very much finishing to get them back in shape.  He's wrong about steel valves, for the most part.  I really don't see them lasting any longer than OEM Ti does, and the spring kits are often as expensive as the valves.

 

And you can actually just replace the one valve. That's what I did when I had the engine opened up for some trans mods and a new piston.  On inspection, it became apparent that the center valve had started to wear noticeably, but none of the others had yet moved, clearance-wise, so that's all I did.



  • Yzflier977

Posted March 23, 2016 - 04:33 PM

#13

I categorically disagree with the service guy's assessment.  If the center intake closed up for the second time, and has moved more than .10mm, it's not going to last very much longer, and it has become a failure risk.  He is right about the seats, provided you don't let the valve go too long.  The don't usually need very much finishing to get them back in shape.  He's wrong about steel valves, for the most part.  I really don't see them lasting any longer than OEM Ti does, and the spring kits are often as expensive as the valves.

 

And you can actually just replace the one valve. That's what I did when I had the engine opened up for some trans mods and a new piston.  On inspection, it became apparent that the center valve had started to wear noticeably, but none of the others had yet moved, clearance-wise, so that's all I did.

So with likely over 200 hours on this head would you just replace the intakes?  Also I noticed no one is mentioning doing anything to the exhaust valves (and FYI they haven't moved since I started checking).  I'm seriously thinking of just replacing the intakes, (if I can get away with intakes only), with OEM.  Mostly because I can use my stock springs so no added cost there.  And if I got over 200 (suspected) hours out of the stockers why not go back?  And if I were to go back with stock intakes would I need to do anything to the head/seats other than just drop them in using new retainers.  I know not to lap Ti valves. Thanks Grey, I appreciate the help.



  • grayracer513

Posted March 23, 2016 - 07:12 PM

#14

YZ450 exhaust valves generally outlast the intakes.  And due to the way the fuel becomes distributed in the 5 valve intake port, the center intake always wears out first.  I would inspect the valves, and reuse those that were in good enough condition.  I reused my own outer intakes and exhausts at around 300 hours. 

 

The center valve you've had to shim will have a distinct, bright band of wear around the face.  It will almost certainly have a detectable ledge, and may be starting to form a "V" in the center.  A valve in good condition will show wear with a less distinctly defined edge, and/or a "blotchy" look, duller grey and with dark patches the color of the valve.  If the wear zone is uniformly bright all the way around, just replace them, even if you can't find an edge.

 

 

Attached Thumbnails

  • CenterIntake.JPG


  • Yzflier977

Posted March 24, 2016 - 05:42 PM

#15

Grey, is there any issue with just replacing the worn valves and re-shimming back to spec?  I was told by one of the head company's I contacted that it isn't advisable to put new Ti coated OEM valves on worn seats as they wouldn't have the matching wear pattern and that would prematurely wear the Ti valves out and I likely wouldn't get the life out of them I would had I replaced them on new seats.  I was also told that if I went back with stainless valves and their springs I could lap them to the old seats with no issues and would get the same life out of them I could expect from new OEM Ti valves with new seats.  New seats and new Yamaha Ti valves would be about $700.  New stainless with new springs on old seats would be about half that.  If I can get away with new Yamaha valves on old seats I'd gladly go that route.  Just don't wanna go back on there for prematurely worn valves in a year.  I appreciate the help.



  • grayracer513

Posted March 25, 2016 - 06:53 AM

#16

You absolutely have to have the seat refinished every time a valve is changed.  Otherwise, you are setting up a condition that will cause the valve to fail; to seal completely and to wear out as much as 3 times faster than it should.  NEVER install a new valve on a worn seat, and absolutely never lap a titanium valve.

 

I also need to point out that if you disassemble the head, the valves and the lifters need to be returned only to their original locations (i.e., left intake to the left intake, etc.) if they are being reused.



  • Yzflier977

Posted March 25, 2016 - 08:34 AM

#17

So valve replacement always involves sending your cylinder head off to have the seats refinished? Even if replacing wih steel valves? Can steel valves be lapped to old seats?

  • WYO522

Posted March 25, 2016 - 10:17 AM

#18

I have a 2013 YZ450F that has stainless steel intake valves and springs that I installed after the stock retainers (in a new GYTR head) began to fail after only 10 hours. I lightly lapped the steel valves into the stock seats and have been running the bike ever since. Last I checked at around 100 hrs everything was in spec. Not saying what I did was right, but like you, I couldn't get a solid answer about lapping steel valves to the stock seats so I did it. So far, so good.


Edited by WYO522, March 25, 2016 - 10:17 AM.


  • Yzflier977

Posted March 25, 2016 - 12:34 PM

#19

What brand of valves did you use? In my thinking you could lap stainless steel valves on old seats and be okay. Just not the Ti ones. Thanks for the reply.

  • WYO522

Posted March 25, 2016 - 01:12 PM

#20

Faction MX is the brand. If I remember right they weren't all that expensive. I bought them on rockymountainatvmc.com





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